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CHAPTER 2 APPLICATION OF PROGRAMMING
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2.5 Operation Processing During Momentary Power Failure
2.5 Operation Processing During Momentary Power Failure
When the input voltage supplied to the power supply module drops below the specified range, the CPU module detects
a momentary power failure and performs the following operation.
(1) When a momentary power failure occurs for a period shorter than the
allowable power failure time
The CPU module registers error data and suspends the operation processing. The CPU module, however,
continues measurement in the timer device and holds the output status.
• When resume start is specified for the SFC program, data in the system is saved.
• The CPU module restarts its operation processing.
• Even if operation processing is suspended due to a momentary power failure, the CPU module continues the
measurement of the watchdog timer (WDT).
When the WDT setting of PLC parameter is 200ms and the scan time is 190ms, if a momentary power
failure occurs for 15ms, "WDT ERROR" occurs.
(2) When a momentary power failure occurs for a period longer than the allowable
power failure time
The CPU module starts its operations initially and the operation processing will be the same as that when either of
the following is performed.
• Powering off and then on the CPU module
• Resetting the CPU modul
Ex.
Ex.
ENDEND
0
END
0
Instantaneous power
failure occurred.
Power recovery
The CPU module suspends
its program operation.
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